1. Field of the Invention
The present invention relates to cathode ray tubes, and more particularly, to a screen for a cathode ray tube, capable of preventing a metal layer, which is formed on a phosphor film coated inside a panel, from expanding and being separated from the underlying layer during a thermal process, and a method for manufacturing the screen.
2. Description of the Related Art
In general, a cathode ray tube (CRT) displays an image by excitation of red, green, and blue phosphors of a phosphor film coated inside a panel by electron beams emitted by an electron gun and passed through electron beam apertures of a shadow mask mounted in the bulb structure formed by the panel and a funnel.
On the inner front surface of a panel, a phosphor film including a black matrix layer and red, green, and blue (RGB) phosphor layer, which are alternately formed as strips, is formed. A metal layer, for example, an aluminum layer, is formed on the phosphor film.
Briefly, a method for manufacturing a screen for the CRT having the structure described above will be described. After cleaning the panel, the black matrix layer and the RGB phosphor layer are sequentially formed inside the panel. Subsequently, a filming layer is formed using an organic material to make the surface of the RGB phosphor layer even. To improve the luminance of the phosphor film and facilitate the emission of excess electrons in the bulb, the aluminum layer is deposited in a vacuum by thermal diffusion.
Next, the filming layer is calcinated so that the organic material is thermally decomposed, emitting gas into the air. This is for preventing energy loss as an electron beam emitted from the electron gun hits the filming layer before landing on the phosphor layer. Formation of the screen inside the panel is complete through a series of processes described above.
In the conventional CRT, the aluminum layer is formed over the entire inner region of the panel to completely cover the phosphor film. This structure has the following problems.
As described above, in forming the filming layer between the fluorescent layer and the aluminum layer to make up fine recessions or air gaps in the phosphor layer, an organic material such as an aqueous emulsion of acrylic resin is evenly spin coated on the phosphor film. The filming layer is removed by means of calcination after the aluminum layer is deposited thereon.
In the deposition of the filming layer inside the panel, it is difficult to evenly control the thickness of the filming layer. It is common that the filming layer is thicker at the edge of the panel, particularly at the corners, than the other inner region of the panel. As a result, a large amount of gas is generated from the relatively thicker region of the filming layer as it thermally decomposes during the calcinations process.
Also, the aluminum layer deposited on the filming layer expands and is separated from the panel while another process is performed or the CRT is operated, so that particles of the aluminum layer block the electron beam apertures up. As the aluminum layer expands, irregular reflection of light occurs at the screen, thereby lowering the luminance of the CRT.